Domain names - concepts and facilities

RFC 1034 §5.3.3 The top level algorithm has four steps:

1. 1. Resolver → Name servers: queries

   The resolver has no answer in local information, so it finds the best servers to ask (its SLIST) and sends them queries until one responds.

   RFC 1034 §5.3.3 3. Send them queries until one returns a response.

2. 2. Name servers → Resolver: better delegation

   A response may be a referral: a better delegation to other servers. The resolver caches it and goes back to choosing the best servers to ask.

   RFC 1034 §5.3.3 b. if the response contains a better delegation to other servers, cache the delegation information, and go to step 2.

3. 3. Resolver → Name servers: queries

   The resolver now queries the servers from the delegation, which are closer to the answer.

   RFC 1034 §5.3.3 3. Send them queries until one returns a response.

4. 4. Name servers → Resolver: answers the question

   When a response answers the question, or says the name does not exist, the resolver caches the data and returns it to the client.

   RFC 1034 §5.3.3 a. if the response answers the question or contains a name error, cache the data as well as returning it back to the client.